SQL Server, Having Clause, Where, Aggregate Functions - sql-server

Question

In my problem which I am trying to solve, there is a performance values table:
Staff PerformanceID Date Percentage
--------------------------------------------------
StaffName1 1 2/15/2016 95
StaffName1 2 2/15/2016 95
StaffName1 1 2/22/2016 100
...
StaffName2 1 2/15/2016 100
StaffName2 2 2/15/2016 100
StaffName2 1 2/22/2016 100
And the SQL statement as follows:
SELECT TOP (10)
tbl_Staff.StaffName,
ROUND(AVG(tbl_StaffPerformancesValues.Percentage), 0) AS AverageRating
FROM
tbl_Staff
INNER JOIN
tbl_AcademicTermsStaff ON tbl_Staff.StaffID = tbl_AcademicTermsStaff.StaffID
INNER JOIN
tbl_StaffPerformancesValues ON tbl_AcademicTermsStaff.StaffID = tbl_StaffPerformancesValues.StaffID
WHERE
(tbl_StaffPerformancesValues.Date >= #DateFrom)
AND (tbl_AcademicTermsStaff.SchoolCode = #SchoolCode)
AND (tbl_AcademicTermsStaff.AcademicTermID = #AcademicTermID)
GROUP BY
tbl_Staff.StaffName
ORDER BY
AverageRating DESC, tbl_Staff.StaffName
What I am trying to do is, from a given date, for instance 02-22-2016,
I want to calculate average performance for each staff member.
The code above gives me average without considering the date filter.
Thank you.

Answer 1

Apart from your join conditions and table names which looks quite complex, One simple question, If you want the results for a particular date then why is the need of having
WHERE tbl_StaffPerformancesValues.Date >= #DateFrom
As you said your query is displaying average results but not for a date instance. Change the above line to WHERE tbl_StaffPerformancesValues.Date = #DateFrom.
Correct me if I am wrong.

Answer 2

Thanks for the replies, the code above, as you all say and as it is also expected is correct.
I intended to have a date filter to see the results from the given date until now.
The code
WHERE tbl_StaffPerformancesValues.Date >= #DateFrom
is correct.
The mistake i found from my coding is, in another block i had the following:
Protected Sub TextBoxDateFrom_Text(sender As Object, e As System.EventArgs) Handles TextBoxDate.PreRender, TextBoxDate.TextChanged
Try
Dim strDate As String = Date.Parse(DatesOfWeekISO8601(2016, WeekOfYearISO8601(Date.Today))).AddDays(-7).ToString("dd/MM/yyyy")
If Not IsPostBack Then
TextBoxDate.Text = strDate
End If
SqlDataSourcePerformances.SelectParameters("DateFrom").DefaultValue = Date.Parse(TextBoxDate.Text, CultureInfo.CreateSpecificCulture("id-ID")).AddDays(-7)
GridViewPerformances.DataBind()
Catch ex As Exception
End Try
End Sub
I, unintentionally, applied .AddDays(-7) twice.
I just noticed it and removed the second .AddDays(-7) from my code.
SqlDataSourcePerformances.SelectParameters("DateFrom").DefaultValue = Date.Parse(TextBoxDate.Text, CultureInfo.CreateSpecificCulture("id-ID"))
Because of that mistake, the SQL code was getting the performance values 14 days before until now. So the average was wrong.
Thanks again.